In the manufacture of semiconductor chips, a workpiece, such as a silicon wafer or other substrate is exposed to a variety of different processes in different processing chambers. The chambers may expose the wafer to a number of different chemical and physical processes whereby minute integrated circuits and micromechanical structures are created on the substrate. Layers of materials which make up the integrated circuit are created by processes including chemical vapor deposition, physical vapor deposition, epitaxial growth, and the like. Some of the layers of material are patterned using photoresist masks and wet or dry etching techniques. The substrates may be silicon, gallium arsenide, indium phosphide, glass, or other appropriate materials.
The processing chambers used in these processes typically include a substrate support, pedestal, or chuck to support the substrate during processing. In some processes, the pedestal may include an embedded heater to control the temperature of the substrate and, in some cases, to provide elevated temperatures that may be used in the process. An electrostatic chuck (ESC) has one or more embedded conductive electrodes to generate an electric field that holds the wafer on the chuck using static electricity.
An ESC will have a top plate, referred to as a puck, a bottom plate or base, referred to as a pedestal, and an interface or bond to hold the two together. The top surface of the puck has a contact surface that holds the workpiece which can be made of various materials, e.g. polymers, ceramic, or a combination, and may have coatings all over or over selective locations, etc. A variety of components are embedded into the puck including electrical components for holding or chucking the wafer, and thermal components for heating the wafer.
Because the circuits and structures formed on the workpiece are very small, the thermal and electrical environment provided by the workpiece support must be very precise. When the temperature is not uniform or consistent across the workpiece, the circuits and structures will have variations. If one support is different from another support, then the circuits and structures will vary with different supports. For extreme cases, the processes may require adjustment for use with different supports. This directly affects the quality and yield of the circuits and structures produced on the workpieces. As a result, a puck with embedded, thermal and electrical components has stringent dimensional requirements, both in-plane and vertical, to ensure consistent performance not only across the surface of a particular ESC but also from one ESC to another ESC.